This invention relates generally to gas turbines and, more particularly, to a catalyst bed which is placed in the exhaust stream of a gas turbine.
In an effort to reduce undesirable emissions such as carbon monoxide, it has become common to provide a catalyst bed at the exhaust to reduce the harmful emissions prior to the exhaust gases being passed through the exhaust stack and into the atmosphere.
It has also become customary to provide a flow of cooling air within the enclosure around a gas turbine and to mix the cooling air with the gas turbine exhaust gases so that the temperatures are reduced when passing through the exhaust silencers and the exhaust stack. It has been recognized that if a catalyst bed is introduced in such an arrangement, that both the turbine exhaust gases and the cooling air pass through the catalyst bed, then the pressure drop through the catalyst would cause excessive pressure rise in the enclosure and reduce the temperature at the catalyst, thereby rendering it less effective.
One conventional approach for solving this problem is to allow the cooling air to flow over the turbine only and not to mix the cooling air with the gas turbine primary air. While this approach reduces the pressure drop across the catalyst and makes it more effective, the benefits of reduced exhaust temperature which would otherwise occur from the mixing of the gases are lost.